Changes Within the Earth

1. Changes Within the Earth 1-2

2. I. Physical Characteristics • A. The Earth’s Layers • 1. Core – center of the earth consisting of very hot metal (mainly iron with some nickel) • a. Inner – dense and solid • b. Outer – molten, liquid • 2. Mantle – thick layer of rock (1,800 miles thick)…mostly solid • 3. Crust – rocky surface layer

3. B. Land, Air, and Water • 1. Lithosphere – soil, rocks, landforms, & other surface features • 2. Atmosphere – layer of air, water, and other substances above the surface • 3. Hydrosphere – water in oceans, lakes, and rivers & under ground • 4. Biosphere – world of plants, animals, and other living things that occupy the planet

4. C. The Planet • 1. 70% of earth’s surface is covered by water • a. Atlantic Ocean • b. Pacific Ocean • c. Indian Ocean • d. Arctic Ocean • e. Southern Ocean

5. 2. Continents – large landmasses in the oceans • a. North America • b. South America • c. Africa • d. Asia • e. Australia • f. Antarctica • g. Europe *largest *smallest

6. D. Landforms - *classified according to differences in relief (the difference in elevation between the highest and lowest points) • 1. mountains – high relief at least 2,000 ft. • 2. hills – lower, rounded, and less steep than mountains • 3. plateaus – raised area with a generally level surface • 4. plains – flat or gently rolling area with few changes in elevation

7. II. Physical Processes • A. Volcanoes • 1. form when magma breaks through the earth’s crust • 2. lava – molten rock

8. B. Movements in the Crust • 1. fold – when rock layers bend and buckle • 2. faults – breaks in the earth’s crust • *whether rock layers fold or fault is determined by the hardness of the rock and the strength of the movement • *large, sudden movements that occur along a fault can cause earthquakes

9. III. Understanding the Past • A. Plate Tectonics • 1. theory that suggests the earth is not one solid sheet of rock • 2. instead, it’s broken into a number of moving plates • 3. the plates vary in size and thickness • 4. the earth’s oceans and continents ride atop the plates as they move in different directions • 5. most earthquakes, volcanoes, & other geological events occur on plate boundaries

11. B. Continental Drift • 1. continental drift theory – the idea that continents slowly shift their positions due to movement of the tectonic plates on which they ride • 2. proposed by Alfred Wegener who said that there once was a single “supercontinent” • 3. Pangaea – the supercontinent that began to break apart 180 million years ago • 4. supported his theory by finding fossils (preserved remains of ancient animals & plants) that were identical from all different continents

13. C. Seafloor Spreading • 1. using sonar, scientists mapped the floor of the Atlantic Ocean and found that the floor was not flat • 2. they found mountains, deep canyons, and wide plains much like what is above water • 3. samples that they took showed that the rocks on the ocean floor were much younger than the rocks above water • 4. seafloor spreading – molten rock from the mantle rises beneath the underwater ridge and breaks through a split at the top of the ridge

15. D. Plate Movement • 1. convection – circular movement caused when a material is heated, expands and rises, then cools and falls • 2. this happens beneath the plates and causes them to move

16. E. When Plates Meet • 1. Spreading – when plates move away from each other • *likely to have rift valley, earthquakes, & volcanic activity • 2. Subduction– when one plate slides underneath another toward the mantle • *the rock melts & many erupt as volcanoes (Andes) • 3. Converging – when two plates collide and neither sink • *buckling, folding, & faulting will produce huge mountain ranges (Himalayas) • 4. Faulting – when plates slip or grind past each other • *causes earthquakes (San Andreas Fault)

17. Subduction Spreading Converging Faulting

18. F. Explaining Volcanoes • 1. Ring of Fire – circle of volcanoes surrounding the Pacific Ocean • 2. volcanic islands can form far away from fault lines • 3. “hot spots” are regions deep in the earth’s mantle where columns of magma rise towards the earth’s surface • a. The magma may heat underground water and produce hot springs or geysers (Yellowstone National Park) • b. If molten rock flows out of a crack in the surface, it may produce a volcanic island chain (Hawaii)